Caption: Nudibranch (Nembrotha kubaryana). Nudibranchs are shell-less marine molluscs that live in seas around the world. They have external gills that give nudibranchs their name, meaning naked gills. The bright colouration seen here acts as a warning to predators that it is toxic. Photographed off Mabul Island, Celebes Sea, Sabah, Malyasia.